I did a search but my HVAC was completely dead and found all signs were FSR as well. Coincidentally I had a regular draw on the battery that would drain it enough that the tender could barely keep up never turning green. Once replaced everything works and tender keeps it charged. 2 issues solved.

It does require some twisting and turning to get up there but theres lots of stuff on internet how to locate and replace and its such a prolific point of failure on these and e39's that most dealers stock multiples.

Good luck